Researchers found that teens who played violent video games ate more chocolate and were more likely to steal raffle tickets in a lab experiment than were those who played nonviolent games.

The effects were strongest in teens who scored high on a measure of moral disengagement - the ability to convince yourself that ethical standards don't apply to you in a particular situation, researchers said.

The results suggest that the risks posed by violent video games goes beyond the well-studied impacts on aggression, said Brad Bushman, co-author of the study and professor of communication and psychology at The Ohio State University.

"When people play violent video games, they show less self-restraint. They eat more, they cheat more," Bushman said.

Bushman conducted the study with colleagues from Italy. Participants were 172 Italian high school students, aged 13 to 19.

They played either a violent video game (Grand Theft Auto III) or a nonviolent game (Pinball 3D or MiniGolf 3D) for 35 minutes, after practising for 10 minutes.

During the experiment, a bowl containing 100 grammes of chocolate candy was placed next to the computer. The teens were told they could freely eat them, but were warned that high consumption of candy in a short time was unhealthy. Those who played violent games ate more than three times as much candy as did the other teens, the result showed.

"They simply showed less restraint in their eating," Bushman said.

After playing the game, the teens were asked to solve a 10-item logic test in which they could win one raffle ticket for each question they got right. The raffle tickets could be used to win prizes.

The teens were told how many answers they got correct and had the opportunity to take the appropriate number of raffle tickets out of an envelope containing many tickets while not being watched.

Results showed that teens who played a violent game cheated more than did those who played a nonviolent game - more than eight times more.

Bushman also measured aggression of players after they had played a video game. The players competed with an unseen "partner" in a game in which the winner got to blast the other person with a loud noise through headphones.

Those who played the violent games chose to blast their ostensible partners with louder noises that lasted longer than did teens who played the nonviolent games.

"We have consistently found in a number of studies that those who play violent games act more aggressively, and this is just more evidence," Bushman said.